Method of and apparatus for reproducing sound



31, 1944- D. A. WHITSON METHOD OF ANDAPPARATUS FOR REPRODUCING SOUNDFiled Aug. 16, 1920 Patented Oct. 31, 1944 METHOD OF AND APPARATUS ron'nsraonocmo SOUND Delmar A. Whitson, Los Angeles, Calii., assignor toWhitson Photophone Corporation, a corporation of Nevada ApplicationAugust 16, 1920, Serial No. 403,709

1 Claim.

My invention relates to the reproduction of sound from a photographicrecord.

The object of the present invention is to provide means for reproducingsound from a record of this character.

Further objects and advantages will be made evident hereinafter.

In the drawing which is for illustrative purposes only,

Fig. l is a diagrammatic section thru one form t of my invention.

Fig. 2 is a view showingthe sound record and the gates therefor. I

Fig. 3 is a view with a distributing sheet,

Fig. 4 is an enlarged section thru said sheet showing the type ofcylindrical lens used.

Fig. 5 is a view of the grid.

Fig. 6 is a view of the plate.

In the embodiment of my invention shown, H is a tube preferably made ofquartz glass and filled .with an inert gas such as argon or neon. Sealedin the walls of the tube ii are three terminals l2, l3 and I4. Carriedon the terminal it is a metallic sheet l5 having a slot It in which acylindrical lens it is placed, this lens entirely filling the slot i8and tending to disperse in a tan shaped form any rays of light passingthrough this slot. Secured on the terminal 13 is a grid is preferablyformed of wire and secured on the terminal M is a plate 20 which hasupon its face a coating 2| of photo-electric material. By photo-electricmaterial I mean a substance such as rubidium which has the capability ofionizing the space adjacent thereto upon being illuminated by a light orviolet ray source of illumination. An exciter battery is connectedbetween the terminals l2 and M and an intoning battery has one terminalconnected to the terminal 13, the other terminal being connected into anaudion amplifier 32 which is connected to the terminal H2, The amplifier32 is connected to some sort of a sound reproducer, such as a loudspeaker, 33. The sound record shown at in Fig. l and Fig. 2 ispreferably a piece of motion picture film, having a band ll composed oflines which'represent the sound record, these lines being of varyingdensity so they will pass more-or less light. A source of illumination43 is provided, the film 4i passing through gates 44 and 45 having slots58 which are adjacent to the slot 15.

The method or operation of my invention is as follows:

The film to is passed between thegates M and 4! at a constant rate ofspeed. The light from the luminous source 43 passes through the openlugs46 and through the film 4|] carried there- "between, the light thenpassing through the walls of the tube H and through the slot l6 where itit spread into a wedge shaped ray which impinges upon the photo-electricsubstance 2 l on the plate 20. The exciter battery 30 sets up anelectric fieldbetween the plate 20 and the sheet i5, this field having acertain resistance which governs the amount of current which may passbetween the grid i8 and the plate or cathode 20. Whenever a light oractinic ray falls upon the photoelectric substance 2|, the substanceemits electrons. causing the space between the grid l8 and the plate 20to be ionized thus changing the resistance of this space and allowingmore or less current to flow through the amplifier 32 which is in serieswith this space and with the intoning battery 36. These electrons areattracted to grid 58, some of them passing through the interstices ofthe grid and striking the sheet or anode 1 l5. This causes secondaryemission from anode it, these secondary electrons being attracted togrid it due to the positive bias on the grid. The amount of thisionizing is proportional to the intensity of the illumination and thisintensity of the illumination is in turn proportional to the light rayswhich produce the markings M on the film. As a result the amplifierdelivers current to the loud speaker 33 which reproduces accurately thesound originally recorded on the film I claim as my invention! Anapparatus for reproducing sound comprising a film printed withtransverse bands proportional to the sound to be reproduced; a closedquartz tube containing an inert gas; a metallic plate in said tube; ametallic sheet in said tube parallel to said plate; ametallic gridbetween said plate and said sheet; an exciting source of electricityconnected to impress an 'electromotive force between said plate and saidsheet; an intoner having one terminal connected to said plate; anintoning source of electricity connected between the other terminal ofsaid intoner and said grid; a layer of photo-electric material on saidplate on the side towards said sheet; a cylinsaid lens, said slot beingcovered by said film;

and a luminous source so placed as to shine through said film, said slotand said lens on said photo-electric material.

DELMAR A. WHITSON.

